Method of grinding gears



May 17, 1932. E. WILDHABER 3 5 METHOD OF GRINDING GEARS Filed Sept. 25, 1926 2 Sheets-Sheet l INVENTOR 1932. I E. WILDHABER 81,858,568 v METHOD OF GRINDING GEARS .Filed Sept. 25, 1926 2 Sheets-:Shet 2 AINVENTOR Patented May 17, 1932 PATENT orrica manner wnnman, or no m You mndn or enmzome ems Application filed September 25, 1926. Serial no. 13mm.

The present invention relates to methods of inding the teeth of gears, namely straight teeth and particularly helical teeth or threads.

teeth with a grindin wheel which may be trued to a single circu ar are.

Another object is to devise a method of grinding teeth with agrindin wheel so positioned as to increase its ri ity and to 1ncrease. the volume of its use 1 abrasive material.

A still other object is to devise a method of the said character, which employs a pair of grindin wheels rotatable-about axes extending in t e same direction.

A further aim is to provide a method for grinding the teeth of a pair of gears, which employs on one gear of said pair a grinding wheel having a convex'circular grinding profile, and on the other gear of said pair a grinding wheel having a concave circular grinding profile.

Another object in view is to provide a method for grinding a pair of helical or herringbone gears with grinding wheels whose profiles are single convex circular arcs and single concave circular arcs respectively, the

radii of said arcs being substantially equal.

Further objects will appear in the course of the specification and in the appended claims. n

While my method variety of gearing, one important application is 'to grinding helical and herringbone gears of thetype disclosed in my application entitled Helical gearing, filed November 2, 1923. Serial No. 672,254. a

My invention will be explained with reference to the accompanying drawings, in which:

Fig. 1 is a. plan view of a pair of grinding wheels in engagement with a blank, said wheels being positioned and shaped according to the present invention.

Fig. 2 is a front elevational' view of the same, corresponding to Fig. 1.

Fig. 3 is a partialvije'w of a pair of grinding wheels in engagement with a gear blank,

is applicable to a greatthe view being taken in the direction of the teeth, which are shown in section.

Fig. 4 is a partial section perpendicular to the teeth of a blank, and a comparative view of grinding wheels of difi'erent positions.

Fi 5 is .a plan view showing a pair of grin ing wheels of convex grinding profile in engagement with a gear blank, which latter may mesh with a pinion as shown in Fig- 00 ures 1 and 2.

Fig. 6 is a view of the grinding wheels shown in .Fig. 5, taken lengthwise of the teeth, which are shown in normal section.

Fig. 7 is a plan view of a machine for 05 practicing my method.

Fig. 8 is a front elevationalview of the same.

Fig. 9 is a side view corresponding to Fig. 8.

, Fig. 10 is a diagram explanatory ofthe operation of the machine shown in the Figures 7, 8, 9.

In Figs. 1, 2 and 3, 11 and 12 denote two coaxial grinding wheels rotatable on an axis 13. and provided with curved grinding s'urfaces 14, 15. These grinding surfaces are outwardly disposed and engage with opposite tooth sides 16, 17 (see Fig. 3) of difierent tooth spaces of a gear blank 18.

Preferably the grinding wheels are trued, with known means, to single circular arcs, as indicated diagrammatically at '19 in Fig. 4, whose radius 20 is smaller than the outside radius of the grinding wheel.

' .Truing to a circular arc is a very sim le operation, which can be performed with high accuracy and thus insures an accurate product.

. It is further noted, that by positioning two wheels so as to grind on opposite tooth sides 00 of different tooth spaces the grinding profile of the wheels'can be made more inclined to a radial plane (22 or 23, Fig. 1 and Fig. 3) than when grinding both sides of a tooth space with a single wheel. This reduces deflections of the grinding wheels, and the grinding wheels are more similar to those used in cylindrical grinding, whose rlgidlty and efliciency is well recognized. For the same reason'the wheels shown in Fig. 3 oifer than an abrasive wheel, which engages both sides of a tooth space simultaneously.

In comparison with flat grinding wheels, which grind with a plane side surface, the

wheels shaped and positioned according to the present invention are more rigid, and offer more rinding stock, comparing wheels of equal iameters. r

Fig. 4 is a section perpendicular to the teeth at a point 25, which is usually a point of the pitch surface. Fig. 4 has particular reference to the type of helical gearing above mentioned. In this gearing, the pinion 26 of a pair of gears is rovided with teeth consisting entire y of a denda, and having circular tooth profiles 27 in normal section, whose cen ters 28 are located on the pitch surface. The gear, or lar r member of the pair (30, Fig. 6) is provi ed with concave circular profiles (31), whose centers are also on the pitch surface and whose profile radii (32) are substantially equal to the profile radii 29 of the pinion.

It has been demonstrated in the application referred to that teeth of this character contact with each other along a whole profile at once, unlike usual gears, namely along the profile (27), whose center (28) just passes through the radius (33) which connects the axes of the two gears. As the gears turn on their axes, the profile along which the contact takes place, moves axially of the gear, passing from one side of the face to the other.

In gearing of this type, a grinding-wheel 34, indicated in dotted lines in Fig. 4, having a circular grinding profile 27, will contact with a pinion blank 26 along said profile 27, if its axis 35 is situated in the plane of the normal section, namely the plane perpendicular to the tooth helix at point 25 of the pitch surface. Axis 35 is perpendicular to radius 33 and is therefore inclined to the plane of the gear, that is a plane perpendicular to the gear axis, b the helix angle of the teeth; in other words y the same angle (H) as the teeth or threads are inclined to the straight generatrices of their pitch surface.

Preferably a grinding wheel (11) is differently and so positioned, that its grinding profile is more inclined to a radial plane. The axis 36 of such a wheel will then include an acute angle 5 with radius 33, and will therefore be less inclined to the plane of the gear blank than axis 35-of the wheel 34. I

The inclination angle H of axis 36 to the plane of the gear blank will now be determined. Angle H is indicated in plan view Fig. 1, where also the helix angle H is shown for comparison.

Inasmuch as the latter plane intersects the drawing plane of Fig. 4 along radius 33, and is inclined to it byisaid angle H, the sine of inclination angle of axis 36 to said plane can be determined by plotting a unit distance (1'3 from point 37 to point 38 on axis 36, and by eterminin the normal distance of point 38 from the p ane of the gear blank. This normal distance divided by the said unit distance (1") equals sin H.

, The distance of point 38 from radius 33 is 1" sin i, and the normal distance of point 38- from'the plane of the gear blank is therefore 1" sin z'Xsin H.

Hence sin H=sin 21X sin H.

In Fig. 5 and Fig. 6 I have shown two grinding, wheels 40,41 having convex circular grinding profiles 42, 43. Profile 42 has a radius 4 and a center 45. It is noted that the center 45 of the profile is at a distance 46 from axis 47, which is smaller than the radius of the wheel 40, whereas the center 48 of the concave profile 19 of-grinding wheel 11 (Fig. 4) is situated at a distance from axis 36 greater than the outside radius of wheel 11.

- The axes 47, 50 of the wheels 40, 41 extend in. the same direction, (see Fig. 5). The same holds true for the axes of the wheels 11 and 12 of Fig. 1 and Fig. 2. In the present case, however, the axes do not coincide, but are shifted apart axially of the gear by such a distance, that the wheels 40, 41 operate on the respective tooth sides at about equal axial position with respect to the gear blank.

Grinding with both wheels at about the same axial location on the gear saves in the length .of axial feed, which is required for finishing the teeth. The savin is increasing'ly pronounced, the larger t e diameter f f the gear blank is in comparison with its ace. 1

By positioning and shapin a pair of grinding wheels as shown in t e drawin namely so that the grinding profile inclu es a considerable .angle with a radial lane, I gain the further advantage, that fmay adjust both wheels in the same direction for truing. This adjustment is preferably effected at right angles to the axes of the wheels, in directions 52, 53v in Figures 3 and 6 respectively. The usual way of adjusting a pair of wheels in the art of grinding gears is in different directions on the two wheels, and not merely at right angles to their axes, but also axially or in an inclined direction.

The profile (19 in Fig. 4) of a grinding wheel may be trued on the side opposite to the grinding contact,'and the truing device is then fed in the same direction 56, as the wheel, as known in the art, and twice as fast. Its feed corresponds to the reduction of the diameter of the wheel, whereas the feed of the wheel itself corresponds to the reduc- ]tion of its radius.

" wheels trued to convex and concave circular part of slide 72. On top of slide72 a slide.

or table 76 is provided, which is movable in a plane. Its radial position is controlled by a slot 77 engaging with a tooth 78, whose angular position is determined by cams 7 9). The axial or lateral position of table 76 is controlled by a helical pinion 80, engaging with rack teeth (80a) of said table 76, so

, that tooth engagement is kept up in different radial positions of said table.

' Slide 76 carries a spindle 81 held in suitable bearings 82, 83. Spindle 81 contains a master gear 84 of equal tooth number and equal lead as the blank. and a brake-85, which somewhat opposes free rotation of spindle 81. Brake 85 is preferably of multiple disk type, running in oil to give smooth action. Brake 85 consists of a housing 86 fastened to table 76, and containing a series of disks 87 which engage with internal splines ofsaid housing and which alternate with disks 88 engaging with external splines of spindle 81. Thevarious disks are under the pressure of a sprin 89.

A blank 90 or two. as shown) is placed on a taper arbor 91, which fits in a taper hole of spindle 81, and on its outboard end is held by dead center 92. Center 92 is kept in postion by a spring (not shown) acting on a ball 93, which presses arm 94 against stop 95. Arm 94 may be swung about pivot 96, for introducing or removing the blank.

Blank 90 engages coaxial grinding wheels 97, which are driven through shaft 98 by an electric motor 99. For simplicitys sake several known details are omitted in the drawings. such as the trui ng device and the means for feedlngthe blank relatively to the grindmg wheels. Motor 99 may be adjusted to the desired angularity (H') on a circular-- guidance 100, and may be fastened with screws engaging T-slot 101.

ihe operation of the machine is as follows:

Table 76 is moved back and forth axially, in the direction of spindle 81, by helical pinion 80. Near or at the end of each complete stroke, table 76 recedes under the influence of tooth 78, and the blank gets out of engagement and out of reach of the grinding wheels 97. It remains out of reach during the (axial) return stroke. If the working stroke is from right to left, Fi 7, and the return stroke from left to rig t, then the blank is being ground while moving axially from right to left, and it clears the grinding wheels while moving from left tori ht.

Fig. 10 shows the blank 90 in wor 'ng engagement with grinding wheels 97, and in the dotted position 90' out of engagement, on the return stroke.

When grinding helical teeth, I always provide during the working stroke afeed between grinding wheel and blank in the direction of the axis of the blank and angularly about said axis. In other Words, the blank performs a helical motion on its axis with reslpect to the grinding wheel.

. uring the working stroke, the master gear 84 engages with a stationary projection 103 in the same manner as a grinding wheel engages the teeth of the blank, or in another suitable manner. The master gear, and with it blank 90, are therefore turned, as they move in the direction of their axis, while brake 85 slides; and the lead of the master gear is reproduced on the blank. During the radial receding motion of table 76' the master gear 84 gets out of engagement with projection 103, and spindle .81 stops turning, prevented by brake 85. Spindle'81 starts to turn again only in the following working stroke, after master gear 84 and projection 103 have come in engagement again.

As the blank turns only during the working stroke, it turns in one direction only, and is therefore indexed in every stroke. The stroke is made of such length, that the blank is indexed by a full number of teeth, and that engagement'between master gear and projection 103 takes place smoothly. This latter engagement starts earlier and lasts longer than the engagement between the blank and the grinding wheels.

' Referring to Fig. 7, the Working stroke starts about, when corner C of table 76 is in dotted position G If so desired, grinding contact may be made on one tooth evenbefore the radial feed of table 76 has been fully completed, and after it has started. that is before and after the blank is at full depth position.

Pinion 80 is secured to hollow shaft 105, which receives oscillatory motion from concentric shaft 106 through a fine tooth clutch 1.07. The latter permits to adjust the axial position of table 76. Shaft 106 carries on its left and an adjustable crank pin, which is oscillated from a shaft 108 by a connecting rod 109. Shaft 108 is journalled on slide 72 and carries on its left end a bevel gear 110 meshing with a bevel pinion 111. Pinion 111 is jo'urnalled in projection 112 of slide 72. and is driven by a shaft 113, which is held in bearings 114, 115 of frame 70, and which can slide endwise in pinion 111. Shaft 113 receives motion from a step pulley 116. While pulley 116 moves uniformly, the pinion $0 is oscillated and in turn reciprocates table Shaft 108 carries on its right end (see Fig. 7) two cams 79, or a double acting cam, operating a forked lever 118, which is connected of the blank 90 member 121 is slightly ahead of the stop 126. Spring 125 presses it against the helical splines 122 and its tooth 78 inwardly against slot 77. During the working stroke table 76 is therefore continuously pressed inwardly, towards the grinding wheels, and against guidance 120, irrespective of inaccurancies in the cams 79.

It is understood that such changes and modifications may be made in my invention as fall within the limits of the appended claims.

I claim as my invention:

1. The method of grinding gears, which consists in providing a gear blank and a grinding wheel trued to a single circular arc, in mounting said grinding wheel on an axis ofi'set from and nonparallel to the axis of said gear blank adjacent the point of nearest approach of the axis of the grinding wheel with respect to the axis of the gear blank, the axial distance of the working surface of said grinding wheel'from said point ofnearest approach being smaller than the outside'radius of said gear blank, in rotating said grinding wheel in engagement with a tooth side of said gear blank, and in providing angular and linear feeding motions between said grinding wheel and said gear blank- 2. The method of grinding gears, which consists in providing a gear blank and a grinding wheel trued to a single circular arc, in mounting-said grinding wheel on an axis offset from and nonparallel to the axis of said gear blank adjacent the point of nearest approach of the axis of the grinding .wheel with respect to the axis of the gear blank, the

axial distance of the workin surface of said grinding wheel from said point of nearest approach being smaller than the outside radius of said gear blank, in rotating said grinding wheel in engagement with a tooth side of said gear blank, and in providing angular and .linear feeding motions between said grinding wheel and said gear blank, said feeding motions consisting .of a translation along a straight line and of a rotation about the axis of the ear blank.

3. T e method of grinding gears, which spaces of said gear blank, in rotating said' grinding wheels,and inproviding feeding motion between said grinding wheels and said gear blank in the direction of the axis of the gear blank and angularly about said axis.

4. The method of grinding gears, which consists in providing a gear blank and a pair of grinding wheels, in mounting said grinding wheels coaxially on an axis offset from and nonparallel to the axis of said gear blank, said grindin wheels being positioned on opposite sides 0 the point of nearest approach of. the axis of the grinding wheels with respect to the axis of said gear blank and having outwardly disposed grinding surfaces, in effecting engagement between said grinding surfaces and two tooth sides of different tooth spaces of said gear blank, in rotating said grinding wheels, and in providing feeding motion between said grinding wheels and said gear blank in the direction of the axis of the gear blank and angularly about said axis.

5. The method of grinding gears having helical teeth, which consists in providing a pair of grinding wheels, in mounting said grinding wheels adjacent a gear blank so that the axis of one grinding wheel extends in the same direction as the axis of the'other grinding wheel, a grinding wheel being disposed adjacent the point of nearestapproach of its axis-with respect to the axis of said gear said gear blank in the direction of the axis of the gear blank and angularly about said axis.

6. The method of grinding gears containing helical teeth, which consists in providing a gear blank and a grinding wheel of curved grinding profile, in mounting said grinding wheel on an axis offset from and angularly disposed to the axis of said gear blank adjacent the point of nearest approach of the axis of the grinding wheel with respect to the axis of the gear blank, the axial distance of thecenter of the working surface of the grinding wheel from said point of nearest approach being smaller than the outside radius of said gear blank and larger than one half of the normal circular pitch of said gear blank, in rotating said grinding wheel in engacgement with said gear blank, and in rovi ing feeding motions between said grin 'ng wheel and said gear blank in the direction of the axis of the gear blank and angularly about said axis. V

7. The method of grinding gears, which consists in positioning a pair of grinding wheels with outwardly disposed grinding surfaces'so as to engage opposite tooth sides of dilferenttooth spaces of a gear blank, in

rotating said grinding wheels on axes extending in the same direction, said axes being ofl:' set from the axis of the gear blank by an amount larger than the outside radius of said gear blank, and in providing feeding motion between said grinding wheels and said gear blank.

8. The method of grinding gears, which consists in providing a pair of grinding wheels having outwardly facing grinding surfaces of curved profile, in positioning saidgrinding wheels so as to operate on oppositely disposed tooth sides of nonadjacent tooth spaces of a gear blank, inrotating said grinding wheels onaxes offset from the axis of the gear blank by an amount larger than the outside radius of the gear blank, and in providing feeding motion between said grind-..

ing wheels and said gear blank.

9. The method of grinding gears contain ing helical teeth, which consists in providing a pair of coaxial grinding wheels trued to curved profiles, in setting the axis of said grinding wheels atan angle to a plane perpendicular to the axis of a gear blank, said angle being smaller than the helix angle of the teeth at the pitch radius, in rotating said grinding wheels in engagement with opposite tooth sides of difierent tooth spaces of a gear blank, and in providing feeding motion be-. tween said grinding wheels and said gear blank in the direction of the axis of the gear blank and angularly about said axis.

10. The method of grinding gears having helical teeth, which consists in providing a grinding wheel having a grinding profile of the form of a single circular arc, the radius ofv said are being smaller than the radius of the grinding wheel, in rotating said grinding wheel adjacent a gear blank, and in providin feeding motions between grinding wheel an gear blank in the direction of the axis of said blank and angularly about said axis.

11. The methodof grinding gears, which consists in providing a pair of grinding wheels having curved active surfaces trued to,

single circular arcs, in rotatin said din wheels in engagement with a blank a di i ti axei extending in the same direction, in providing feeding motions between said grinding wheels and said blank. In testimonywhereof-I afiix my si ERNEST WILD ER.

ature. 

